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Module 6 Flashcards

1
Q

What is a capacitor

A

2 metallic plates seperated by an insulator

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2
Q

Define dielectric

A

Insulator seperating 2 plates in a capacitor

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3
Q

How does a capacitor store charge

A

When the capacitor is connected to the cell, electrons flow from the cell.
The breif current means electrons are removed from plate A of the capacitor and deposited onto the other plate B. Plate A becomes positively charged (loss of electrons) and plate B becomes negatively charge.

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4
Q

What happens when a capacitor is charged

A

The plates have equal and opposite charge (Q) so there is a p.d. across the plates

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5
Q

When is the equation X=Xo (1-e^-t/RC) used

A

when X can be either V or Q

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6
Q

What type of current is the domestic supply

A

Alternating

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7
Q

What is smoothing capacitors

A

A diode is used to make an alternating current flow only in one direction
With a capacitor the output voltage is smoothed out

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8
Q

What is a feild

A

A region in which an object experiences a force

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9
Q

State coulombs law

A

Any 2 point charges exert an electrostatic force on each other that is directly proportional to the product of their charges and inversly proportional to the square of the distance between them

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10
Q

Similarities between electric feilds and gravitational feilds

A

Both are radial feilds
Both follow inverse square law

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11
Q

Differences between electric feilds and gravitational feilds

A

Gravitational feild is always attractive

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12
Q

For a charged particle in an electric feild how is the horizontal motion affected

A

No acceleration (constant v)

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13
Q

For a charged particle in an electric feild how is the vertical motion affected

A

Acceleration = F/m or EQ/m
Suvat can be used

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14
Q

How to find work done from force distance graph

A

Area underneath

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15
Q

Define electric potenitial

A

Electric potential at a point is equal to the work done per unit charge in bringing a positive charge from infinity to that point

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16
Q

Define electric potential difference

A

Work done per unit charge between two points around the particle of charge Q

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17
Q

What is an equipotential line

A

A line along which electric potential is the same

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18
Q

Where do magnetic feild lines act around the earth

A

From South of the earth to north
(north magnetic pole to south magnetic pole)

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19
Q

What rule determines the direction of a magnetic feild

A

Right hand grip rule

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20
Q

Define magnetic flux density

A

The strength of the feild

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21
Q

How does a velocity selector work

A

2 parallel horizontal plates connected to a power supply produces a uniform electric feild between the plates (strength E)
A unifrom magnetic feild (strength B) is applied perpendicular to the electric feild.
The charged particles travelling at different speeds can be sorted through a narrow slit.
Since electric and magentic fields deflect them in opposite directions, only particles witha a specific speed will the directions cancel out.
Only particles with this specific speed will pass through the second slit.

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22
Q

How does a mass spectrometer work

A

Only particles with the same velocity enter a unifrom magnetic feild
Each ion is deflected a different amount by the detector to fin mass

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23
Q

What is a hall probe

A

Used to measure magnetic flux density

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24
Q

Define magnetic flux

A

The product of the component of the magnetic flux density perpendicular to the cross sectional area.

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25
Define magnetic flux linkage
The product of the number of truns in the coil and the magnetic flux
26
SI unit of flux linkage
Weber
27
State Faradays law
The magnitude of the incident emf is directly proportional to the rate of change of magnetic flux linkage
28
State Lenz law
The magnitude of the incident emf is inversely proportional to the rate of change of magnetic flux linkage
29
What is a step up transformer
Has mor turns on the secondarly coil than the first
30
What is a step down transformer
Has fewer turns on the secondary coil than the primary
31
Conclusion of ruthorfords alpha scattering experiment
Most of the alpha particles passed straight through so most of the atom is empty space with most of the mass concentrated in the nucleus Alpha particles near th nucleas were repelled so the nucleus must be positively charged
32
What is an isotope
Nuclei of the same element that have a different number of neutrons
33
What is the nucleon number
Total number of protons and neutrons
34
What is the atomic number
Number of protons present
35
What is the atomic mass unit
1.66x10^-27 or 1 twelfth of the mass of a carbon 12 atom
36
What is the nuckear strong force
Attractive gravitational force between the protons (overcoming magnetic repulsion)
37
Under what range is the strong force attractive
0.5-3fm
38
What is the weak nuclear force
Responsible for beta decay
39
What are hadrons
Particles and antiparticles affected by strong nuclear force and weak nuclear force Made up of quarks (protons, neutrons and mesons)
40
Leptons
Particles and antiparticles unaffected by strong nuclear force (electrons, neutrinos, muons)
41
What are the fundemental particles
Quarks and leptons
42
Types of quarks
up down strange charm top bottom
43
What are baryons
Hadroms made of 3 quarks
44
What are mesons
Hadrons made from quark antiquark pair
45
Beta minus decay
Neutron = proton + electron + electron antineutrino
46
Beta plus decay
proton = neutron + positron + electron neutrino
47
Explain alpha radiation
2 protons and 2 neutrons highly ionising not penetrating (stopped by a sheet of paper) positively charged
48
Explain beta radiation
Fast moving electrons or positrons stopped by 1-10mm of aluminium positively and negatively charged depending on type
49
Explan gamma radiation
High energy photons not very ionising highly penetrating (stopped by 1-10cm of lead) uncharged so unaffected by magnetic feilds
50
Define random
Cannot predict when next decay will be each nucleus has equal chances of decaying per unit time
51
Define spontanious
Unaffected by presence of other nuclei in the sample Unaffected by external factors such as pressure
52
Define half life
Time taken for number of active nuclei in a sample to half
53
Define activity
Rate at which nuclei decay
54
Define decay constant
Probibility of decay of an individual nucleus per unit time (A/N) (lambda in the booklet)
55
How does carbon dating work
Measuring ratio of carbon 14 to carbon 12 of dead material and similar living material.
56
What is annihilation
When a particle and antiparticle meet and their mass is turned into energy
57
Define mass defect
Difference between the mass of the completely seperated nucleaons and the mass of the nucleus
58
Define binding energy
Minimum energy required to completely separate a nucleus into its seperate protons and neutrons
59
what does high binding energy per nucleon
The more tightly bound the nucleons within the nucleus are
60
Define nuclear fission
An unstable uranium 235 nuclei splits into 2 halves after absorbing a nutron Also releases more neutrons
61
What is a moderator used for in a fission reactor
Slow down fast paced neutrons
62
What is a control rod used for in a fission reactor
Material to absorb neutrons
63
What is nuclear fusion
Bring nuclei within 10^-15 fm so strong nuclear force becomes attractive Has to be at high enough temperatures
64
What is thermionic emmision
emission of electrons througb heating at the cathode
65
What is the anode in an X ray
Target metal such as tungsten (high melting point) Undergoes attenuation mechanisms
66
Define simple scatter
Range of 1-20keV X ray photon bounces off
67
Define photoelectric effect in X rays
less than 100keV X ray photon is absorbed and electron is released
68
Define compton scattering
0.5-5MeV Electron is released and X ray released with reduced energy
69
Define pair production
>1.02MeV X ray dissapears and creates electron and positron
70
Define contrast medium
Elements with large atomic numbers so higher attenuation coefficient Barium for digestive system Iodine for blood flow
71
What is a CAT scan
Fan shaped beam of X rays absorbed at the other side by detectors X rays attenuated by different amounts by different tissues Fan complets 360 degrees and table is moved through the ring a bit more
72
Downsides of CAT scans
Ionising expensive time consuming
73
Positives of CAT scans
3D image can distinguish between different tissues
74
What is a radioisotope
Gamma source w short half life placed inside the patient Eg florine 18
75
What is a radiopharmecutical
Medical tracer which is a radioisotope made to reach the correct place Concentrations can identify irregularities in the body
76
Define colimator
Honeycomb of long thin tubes Any photons arriving at an angle are absorbed
77
Define scintillator
Produces viable light from incoming x ray photons
78
Define photomultiplier
Viable light from scintillator is multiplied into a voltage to be connected to a computer and modelled
79
What is a PET scan
Gamma radiation used to make 3d image Use a medical tracer that our body thinks is glucose (flourodeoxyglucose)
80
Advantages of PET scan
3d image non invasive
81
Disadvantages of PET scan
Expensive tracers and equipment
82
Ultrasound benefits
non ionising non invasive
83
What is the peizoelectric effect
peizocrystel compressed and streched produces an alternating current and vice versa The frequency of oscillation is the natural frequency of the crystal
84
Define transducer
used to detect ultrasound
85
What is an A scan
Simple ultrasound Each pulse of ultrasound is partially reflected by different tissues which is recieved at the transducer and displayed on an oscilloscope speed and time used to measure distance
86
What is a B scan
2D image each position of transduce produces a row of dots which corresponds to a boundry brightness of the dot is proportional to intensity of reflected ultrasound computer can turn this into an image
87
What is coupling gel
gel with similar acoustic impedance to skin which stops relfections at skin boundry (impedance matching)
88
What is a doppler ultrasound used for
track blood clots, movement of blood and speed
89
How does intensity effect realeased photon energy
It doesnt photon energy is inependent of intenisty
90
voltage in x rays
High voltage
91
Electrons thru graphite show what
electrons travel in waves
92
Current used in transformers
alternating

Physics (26 decks)

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